Catalytic domain of Fungal Pat1-like Serine/Threonine kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily is composed of Schizosaccharomyces pombe Pat1 (also called Ran1), Saccharomyces cerevisiae VHS1 and KSP1, and similar fungal STKs. Pat1 blocks Mei2, an RNA-binding protein which is indispensable in the initiation of meiosis. Pat1 is inactivated and Mei2 activated, which initiates meiosis, under nutrient-deprived conditions through a signaling cascade involving Ste11. Meiosis induced by Pat1 inactivation may show different characteristics than normal meiosis including aberrant positioning of centromeres. VHS1 was identified in a screen for suppressors of cell cycle arrest at the G1/S transition, while KSP1 may be involved in regulating PRP20, which is required for mRNA export and maintenance of nuclear structure. The Pat1-like subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.
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